1. Field of the Invention
The present invention is directed to a process for removing undesirable material from teeth using micro air abrasion dentistry. More specifically, the invention is directed to an abrasive composition used in a process that effectively removes both hard and soft oral materials including carious enamel, dentin, cementum and spent amalgam.
2. Background of the Prior Art
Aluminum oxide or alumina is one of the largest volume pure chemical compounds produced. It is used widely in industrial and commercial applications from abrasives and ceramics to various medicinal compositions and oral preparations, including toothpaste.
In the relatively new field of micro air abrasion dentistry, alumina is a material often used for painless dental procedures. Rosenberg, in the July, 1996 issue of Dentistry Today refers to micro air abrasion as the new standard in dental care. This article enumerates many advantages realized in micro air abrasion including increased patient comfort, alleviation of patient anxiety, decreased use of anesthesia, increase of dentists' productivity, and decreased costs to both patients and dentists.
Air abrasion tools have similarly been available for use by dentists for treating patients with an abrasive-laden fluid. Such fluids include abrasive-laden air directed onto the patient's teeth for such procedures as removal of decay, preparing the teeth to receive fillings, prophylactic treatment, and the like. Such abrasion devices provide advantages over conventional dental drills. These include eliminating the heat, noise, and vibration produced by conventional high-speed drills. Also eliminated is the need for anesthesia as well as the need to cool the drill with fluid
The early air abrasion micro dentistry materials utilized industrial standard 27 and 50 micron alumina particles. The prior art abrasive materials are not treated for biological purification. Research by applicant has shown that treating the alumina-based abrasive composition for biological inactivity resulted in totally unexpected improvements in its performance in air micro abrasion dentistry.
Using abrasives carried in a fluid stream to remove unwanted oral material is not new. Rzewinski, in U.S. Pat. No. 4,494,932 discloses an air abrasion apparatus and method for cleaning teeth, specifically removing difficult stains and heavy plaque using an unspecified soluble powder. Karst, in U.S. Pat. No. 4,950,160 discloses an air abrasion material for polishing teeth using an unspecified abrasive powder. Other references to the use of the micro air abrasion technique for prophylactic treatment is discussed by Goldstein et al in the Journal of the American Dental Association, Vol. 126, pp 761-766, 1995. In this article, the use of sodium bicarbonate slurry is disclosed to remove stains from teeth.
Goldsmith, in U.S. Pat. No. 5,275,561 discloses a fluid abrasion method for preparing a tooth structure for bonding a composite to the prepared surface using aluminum oxide as the abrasive material. Goldsmith claims a range of particle sizes of alumina ranging from 2 to 100.mu.. He does not mention any optimum particle size, nor does he mention any distribution of particle size. FIG. 2 shows that the particle size distribution of typical alumina abrasive is very scattered; the data in Table 2 analytically verifies the scattered particle size distribution of the prior art alumina.
A process for the removal of soft tooth decay with an abrasive fluid stream was disclosed by the applicant in U.S. Pat. No. 5,601,430. In this patent, the process uses abrasive particles of a non-toxic thermoset plastic, such as a urea resin, for removing areas of tooth decay and preparing the tooth structure for bonding with a filler material. Applicant was not successful using ordinary alumina in removing soft undesired material such as soft caries.
One of the problems associated with some of the abrasives used in micro air abrasion dentistry is that the same abrasive has traditionally been utilized to cut a multitude of materials. Such materials include both healthy and carious enamel, healthy and carious dentin, cementum, amalgam, composite, glass ionomer, copolymer, cements, porcelain, gold, and other metals.
Traditionally, `pure` alumina has been used in micro air abrasion dentistry as an abrasive. This material is effective in cutting hard dental materials, including healthy parts of teeth, as well as porcelain and other hard materials listed above. It is, however, less effective on softer materials. Such softer materials that need removal include carious enamel, carious dentin, cementum, spent amalgam, stains, calculus, materia alba, organic plug, composites, resin restoratives, and the like.
The removal of spent amalgam is of particular interest to the dental community. It is comprised of several metals, one of which is mercury, often used for dental restorations. Concern over the efficient and safe removal of these restorations is related to patient exposure to elemental mercury.
In an article in the March/April 1997 issue of Dental Practice & Finance, Bob Kehoe authored an article entitled "Assessing Air Abrasion". This article, which is intended to provide advice on the use of micro air abrasion, states that micro air abrasion is "designed to conservatively cut virgin teeth, remove sealants and composite restoration, not amalgam or other metals." In light of this recent assessment, the results of the applicant in removing amalgam with micro air abrasion tools and the composition of the instant invention is quite surprising and remarkable.
Applicant's issued patent U.S. Pat. No. 5,601,430 refers to this fact. In this patent, aluminum oxide is stated to remove hard caries material and healthy tooth structure but to be inefficient in removing soft caries material from decayed tooth structure.
Color has been used previously in certain dental air abrasive systems. In U.S. Pat. No. 5,334,019 Goldsmith et al describe adding fluorescent or colored materials to identify and differentiate between several simultaneously used gas streams. Use of color in the instant invention is for the purpose of caries detection. The use of color in the present invention is also being considered to make the abrasive material easily distinguishable from tooth structure to facilitate clean-up after the dental procedures are completed. Furthermore, since applicant is concerned with only one abrasive stream, use of color in the present application is patentably distinct from the prior use.
It is an object of this invention to provide a process using a micro air abrasion instrument and an abrasive that effectively cuts a variety of soft dental materials, including carious enamel, dentin, cementum, and spent amalgam. It is a farther object of the instant invention to provide an abrasive treated for biological inactivity. Prior art materials used for micro air abrasion have not been so treated. Examples of successful biological treatments include but are not limited to treatment with ethylene oxide, dry heat autoclave sterilization, or gamma radiation. Microbiological, chemical, and scanning electron microscopic analyses, as will be seen in the Examples, reveal significant differences in purity and particle size distribution between treated and non-treated abrasive materials.
An even further object of this invention is to provide flavored dental abrasive materials. Since anesthetic is seldom used in micro air abrasion dentistry, use of flavored abrasive material would add to the pleasing aspect of the procedure.
Another object is to furnish the abrasive with a dye that would indicate the presence of caries by the development of color. The colorant may also be used to easily distinguish the abrasive particles from the teeth. This would facilitate clean-up after treatment.
The above remarks establish the need in the art for new and improved formulations for micro air abrasion dentistry. The above discussion furthermore emphasizes the uniqueness of the composition and performance characteristics of the instant invention.